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Wed, 03 Dec 2025 03:21:36 -0800 (PST) Received: from localhost ([2a01:4b00:b703:c200:1ac0:4dff:fe39:5426]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-4792a8ccdfbsm43945665e9.14.2025.12.03.03.21.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Dec 2025 03:21:36 -0800 (PST) From: Punit Agrawal To: Ben Horgan Cc: Punit Agrawal , james.morse@arm.com, amitsinght@marvell.com, baisheng.gao@unisoc.com, baolin.wang@linux.alibaba.com, bobo.shaobowang@huawei.com, carl@os.amperecomputing.com, catalin.marinas@arm.com, dakr@kernel.org, dave.martin@arm.com, david@redhat.com, dfustini@baylibre.com, fenghuay@nvidia.com, gregkh@linuxfoundation.org, gshan@redhat.com, guohanjun@huawei.com, jeremy.linton@arm.com, jonathan.cameron@huawei.com, kobak@nvidia.com, lcherian@marvell.com, lenb@kernel.org, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, lpieralisi@kernel.org, peternewman@google.com, quic_jiles@quicinc.com, rafael@kernel.org, robh@kernel.org, rohit.mathew@arm.com, scott@os.amperecomputing.com, sdonthineni@nvidia.com, sudeep.holla@arm.com, tan.shaopeng@fujitsu.com, will@kernel.org, xhao@linux.alibaba.com, reinette.chatre@intel.com Subject: Re: [PATCH v6 00/34] arm_mpam: Add basic mpam driver In-Reply-To: (Ben Horgan's message of "Thu, 27 Nov 2025 14:25:28 +0000") References: <20251119122305.302149-1-ben.horgan@arm.com> <877bvfa23i.fsf@stealth> Date: Wed, 03 Dec 2025 11:21:35 +0000 Message-ID: <87sedrlsjk.fsf@stealth> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjAzMDA5MCBTYWx0ZWRfX80PeNkuG86oT KBgAUWmu48OXZ5avCTUsqXqiCSUGKrAqUpvOGRCcoDPawvaUW4kNZnqUm63YuI82ND0ZccIQ8bG YQR9BAZqgZuJIcs0B8rLgjs80UJMLqTRz0m4dNuxH35b7W1zPWiZsJPXhnbNQJ1BXrddh06vyAx oTbx2iyw2JZvh8T3LhfmNaptxgPXnvdOa8mLYLzwsb+eXjv4jS1nN011llCWh82f7X1TODIbdIC Jx/ijR4CViHDDV8otmK9z+d488o0Q+SjQhEmQAp76HouQtNc7RFixx/XU53sgMlBMws/eYT3B4j 4hXLMJDgHJ+nHZKiQCXgPWcMp8FNrQScJz/2b1qj1qabvgWER7QHOglrdhCAS0eJ/cG3+NZuy0d s15WIJJhvKupRvrDcQQXXOU8AK6nXg== X-Authority-Analysis: v=2.4 cv=JY6xbEKV c=1 sm=1 tr=0 ts=69301d42 cx=c_pps a=50t2pK5VMbmlHzFWWp8p/g==:117 a=xqWC_Br6kY4A:10 a=wP3pNCr1ah4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=7CQSdrXTAAAA:8 a=2TOxWa3ygJBVc2Mkyu0A:9 a=IoWCM6iH3mJn3m4BftBB:22 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-GUID: 2PNto8oRLaqalRrfCLFpJSMm5LP3sEMU X-Proofpoint-ORIG-GUID: 2PNto8oRLaqalRrfCLFpJSMm5LP3sEMU X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-12-02_01,2025-11-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 adultscore=0 impostorscore=0 suspectscore=0 priorityscore=1501 malwarescore=0 bulkscore=0 lowpriorityscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2510240001 definitions=main-2512030090 Hi Ben, Thanks for getting back. Ben Horgan writes: > Hi Punit, > > On 11/24/25 15:21, Punit Agrawal wrote: >> Hi Ben, James >> >> Ben Horgan writes: >> >>> >>> This series is based on v6.18-rc4, and can be retrieved from: (no v6 version) >>> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git mpam/driver/v5 >>> >>> The rest of the driver can be found here: (no v6 version) >>> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git mpam/snapshot/v6.18-rc4-v5 >>> >>> What is MPAM? Set your time-machine to 2020: >>> https://lore.kernel.org/lkml/20201030161120.227225-1-james.morse@arm.com/ >> >> Although a little late to the party, I've managed to throw together >> enough firmware to describe the MPAM hardware and take this set (more >> specifically mpam/snapshot/v6.18-rc4-v5 branch from James' repository) >> for a spin. Using the branch, the kernel is able to probe the hardware >> and discover the advertised features. Yay! We are in business. > > Thanks for giving it a go. :) > >> >> Having said that, there are a few quirks of the platform that run into >> issues with later patches in the branch. The platform has MSCs attached >> to shared L2 caches which are being skipped during later stages of >> initialisation. IIUC, the L2 MSCs' limitations stems from the >> assumptions in the resctrl interface. > > What in particualar is being skipped? The registration of the discovered MSCs with resctrl and subsequent exposing it to the user. >> I was wondering if there are any patches available to relax these >> limitations? I can give them a try. Or do these need to be put together >> from the ground up? Any pointers greatly appreciated. > > There are some extra things added in the extras branch [1] e.g. cache > maximum usage controls (cmax). However, lots of possible things are > still missing e.g. any monitors on L2. If it doesn't fit with the > topology expected by resctrl then it is unlikely to have been considered > yet. Thanks for the pointer. I'll give the snapshot+extras branch[1] a try. The platform does have both controls and monitors attached to L2. If this isn't being looked at, I can try and put something together. Thanks for confirming that the limitation is likely due to resctrl. Looking forward to the next set of MPAM support landing. > [1] https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/log/?h=mpam/snapshot%2bextras/v6.18-rc1 [...]